1. Field of the Invention
The present invention relates to plastic pumps and more particularly to a cooling arrangement for a sealing member utilized in a plastic pump.
2. Description of the Prior Art
In the construction of pump bodies, it has become desirable, as is the case with many other types of devices, to utilize plastic materials in lieu of conventional metal materials to effectuate cost savings for both material and fabrication labor, as well as to provide lighter weight pumps and to provide other benefits of plastic over metal such as resistance to corrosion. However, one benefit that metal has over plastic is that it is heat conductive. In a pump there is a mechanical seal which prevents a flow of pumped liquid between the pump chamber which generally is filled with liquid, and thus comprises a wet zone, and the outside of the pump body which comprises a dry zone. The seal usually comprises a rotating part and a stationary part, particularly in centrifugal pumps, and thus there is a heat build up due to the frictional rubbing of the seal stationary part against the rotating part. With conventional metal pump bodies, the heat would be dissipated through the pump housing itself, thus reducing or avoiding the problem of heat build up when there is no liquid within the pump body to dissipate the heat, that is, when the pump is not primed. However, with plastic pumps, the plastic pump body cannot dissipate the heat when the pump body is not filled with the liquid to be pumped and thus, there is a danger of damaging the seal due to heat build up.
U.S. Pat. No. 3,826,589 recognizes this problem and provides a solution of incorporating a metallic shield having a base secured to one of the plastic housing sections, and having the body of the shield extending outwardly within the wet zone of the pumping chamber so that it will extend into an area where water is trapped within the pumping chamber to provide the cooling necessary to prevent damage to the seal. However, the shield is held in a non rotating position, and if the water level within the pump housing is not at the level indicated, the necessary cooling may not be provided.